Ball grid arrays (BGA) were introduced a few years ago and typically include a platform on which an integrated circuit is mounted. Conductive traces in the platform connect the integrated circuit to low inductance conductive balls or bumps on the underside of the platform. U.S. patents that are representative of the state of the ball grid array art include U.S. Pat. Nos. 5,045,921 (Lin, et al.), 5,216,278 (Lin, et al.), 5,468,999 (Lin, et al.) and 5,640,047 (Nakashima).
While ball grid arrays initially found acceptance, their use is apparently tapering off due to issues related to product testing. In today's high through-put electronics assembly and manufacturing facilities, it is necessary that assembled and sub-assembled products be readily testable to determine the source of a problem.
Ball grid arrays are used in high frequency, small scale environments where size constraints and issues related to electromagnetic interference (EMI) and radio frequency interference (RFI) create testing problems. It is difficult to find sufficient space for attachment of a probe head to a printed circuit board near a ball grid array. When this is achieved, the test equipment and printed circuit board traces act as radiating antennas introducing unacceptable EMI/RFI.
Hence, there is no effective way to probe ball grid array packages and the like and this has led to their use for some products being disfavored.